Search Publications
The Complex Space Weather Events of 2017 September
Hajra, Rajkumar; Tsurutani, Bruce T.; Lakhina, Gurbax S.
Interplanetary coronal mass ejections (ICMEs), magnetic clouds (MCs), sheaths, corotating interaction regions (CIRs), solar wind high-speed streams (HSSs), fast forward shocks (FSs), reverse waves (RWs), stream interfaces, and heliospheric current sheet crossings detected upstream of the Earth and their geoeffectiveness are studied during 2017 Sep…
Dual-wavelength ALMA Observations of Dust Rings in Protoplanetary Disks
Pascucci, Ilaria; Herczeg, Gregory J.; Wilner, David J. +13 more
We present new Atacama Large Millimeter/submillimeter Array observations for three protoplanetary disks in Taurus at 2.9 mm and comparisons with previous 1.3 mm data both at an angular resolution of ∼0"1 (15 au for the distance of Taurus). In the single-ring disk DS Tau, double-ring disk GO Tau, and multiring disk DL Tau, the same rings are detect…
A Comparison of Flare Forecasting Methods. IV. Evaluating Consecutive-day Forecasting Patterns
Leka, K. D.; Gallagher, Peter T.; Murray, Sophie A. +21 more
A crucial challenge to successful flare prediction is forecasting periods that transition between "flare-quiet" and "flare-active." Building on earlier studies in this series in which we describe the methodology, details, and results of flare forecasting comparison efforts, we focus here on patterns of forecast outcomes (success and failure) over …
A Blueprint for the Milky Way's Stellar Populations: The Power of Large Photometric and Astrometric Surveys
Beers, Timothy C.; An, Deokkeun
Recent advances from astronomical surveys have revealed spatial, chemical, and kinematical inhomogeneities in the inner region of the stellar halo of the Milky Way. In particular, large spectroscopic surveys, combined with Gaia astrometric data, have provided powerful tools for analyzing the detailed abundances and accurate kinematics for individu…
Persistent Starspot Signals on M Dwarfs: Multiwavelength Doppler Observations with the Habitable-zone Planet Finder and Keck/HIRES
Cochran, William D.; Endl, Michael; Mahadevan, Suvrath +23 more
Young, rapidly rotating M dwarfs exhibit prominent starspots, which create quasiperiodic signals in their photometric and Doppler spectroscopic measurements. The periodic Doppler signals can mimic radial velocity (RV) changes expected from orbiting exoplanets. Exoplanets can be distinguished from activity-induced false positives by the chromaticit…
Determination of the Local Hubble Constant from Virgo Infall Using TRGB Distances
Lee, Myung Gyoon; Kang, Jisu; Jang, In Sung +1 more
An independent determination of H0 is crucial given the growing tension between the Hubble constant, H0, derived locally and that determined from the modeling of the cosmic microwave background (CMB) originating in the early universe. In this work, we present a new determination of H0 using velocities and tip of th…
The Leoncino Dwarf Galaxy: Exploring the Low-metallicity End of the Luminosity-Metallicity and Mass-Metallicity Relations
Cannon, John M.; Dolphin, Andrew E.; Skillman, Evan D. +10 more
Extremely metal-poor (XMP) galaxies are low-mass, star-forming galaxies with gas-phase oxygen abundances below 12 + log(O/H) = 7.35 (∼ 1/20 Z⊙). Galaxy evolution scenarios suggest three pathways to form an XMP: (1) secular evolution at low galaxy masses, (2) slow evolution in voids, or (3) dilution of measured abundances from infall of …
EvryFlare. II. Rotation Periods of the Cool Flare Stars in TESS across Half the Southern Sky
Law, Nicholas M.; Corbett, Hank; Fors, Octavi +6 more
We measure rotation periods and sinusoidal amplitudes in Evryscope light curves for 122 two-minute K5-M4 TESS targets selected for strong flaring. The Evryscope array of telescopes has observed all bright nearby stars in the south, producing 2-minute cadence light curves since 2016. Long-term, high-cadence observations of rotating flare stars prob…
O2- and CO-rich Atmospheres for Potentially Habitable Environments on TRAPPIST-1 Planets
Hu, Renyu; Wolf, Eric T.; Peterson, Luke
Small exoplanets of nearby M-dwarf stars present the possibility of finding and characterizing habitable worlds within the next decade. TRAPPIST-1, an ultracool M-dwarf star, was recently found to have seven Earth-sized planets of predominantly rocky composition. The planets e, f, and g could have a liquid water ocean on their surface given approp…
ALMA Evidence for Ram Pressure Compression and Stripping of Molecular Gas in the Virgo Cluster Galaxy NGC 4402
Rubio, M.; Pompei, E.; Vlahakis, C. +5 more
High-resolution (1″ × 2″) Atacama Large Millimeter Array CO(2-1) observations of the ram pressure stripped galaxy NGC 4402 in the Virgo cluster show some of the clearest evidence yet for the impacts of ram pressure on the molecular interstellar medium (ISM) of a galaxy. The eastern side of the galaxy at r ∼ 4.5 kpc, upon which ram pressure is inci…